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© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois.

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Presentation on theme: "© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois."— Presentation transcript:

1 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois by Russell Krick

2 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

3 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Basic brake system  Braking ratio  Brake system hydraulics  Brake system components  Parking brakes

4 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Automotive Brakes  Provide a means of using friction to slow, stop, or hold the wheels of a vehicle  When a car is moving, it has kinetic energy (inertia)  To stop the vehicle, the brakes convert mechanical (moving) energy into heat

5 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

6 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Operation  When the driver pushes on the brake pedal, lever action pushes a rod into the brake booster and master cylinder  The pressure developed in the master cylinder forces fluid through the brake lines to the wheel brake assemblies  The brake assemblies use this pressure to cause friction for braking

7 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Parking Brake  The parking brake system uses cables or rods to mechanically apply the rear brakes  Provides a system for holding the wheels when the vehicle is parked on a hill or stopping the vehicle during complete hydraulic brake system failure

8 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Drum and Disc Brakes  Two common types of brake assemblies:  Disc brakes  often used on the front wheels  Drum brakes  often used on the rear wheels

9 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Drum and Disc Brakes Disc brakesDrum brakes

10 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Comparison of front wheel braking effort to rear wheel braking effort  When a vehicle stops, its weight tends to transfer onto the front wheels  The rear tires lose some of their grip  The front wheels must do more of the braking

11 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Typical Braking Ratios  Rear-wheel-drive vehicles:  front brakes may handle 60% to 70% of the braking, rear brakes handle 30% to 40%  Front-wheel-drive vehicles:  more weight is concentrated on the front wheels  braking ratio is even higher at the front wheels

12 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Automotive brakes use a hydraulic system  Hydraulic brakes use confined brake fluid to transfer brake pedal motion and pressure to each of the wheel brake assemblies

13 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic Principles  Liquids in a confined area will not compress  When pressure is applied to a closed system, pressure is exerted equally in all directions  Hydraulics can be used to increase or decrease force or motion

14 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic System Action  Pressure and motion can be transferred from one cylinder to another  Cylinders of the same size:  if one piston is moved, the other will move the same amount with the same force  Cylinders of different sizes:  if the smaller piston is moved, the larger piston will move with more force, but it will move a shorter distance

15 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic System Action In a hydraulic jack, a small piston acts on a large piston, resulting in great force, but a small amount of movement

16 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic System Action Hydraulic jack operation

17 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic Brake Action  The master cylinder acts as the pumping piston that supplies system pressure  The wheel cylinder acts as the power piston, moving the friction linings into contact with the rotating drums or discs

18 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic Brake Action

19 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

20 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Pedal Assembly A lever arm to increase the force applied to the master cylinder piston

21 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder  Foot-operated pump that forces fluid to the brake lines and wheel cylinders  Develops pressure to apply the brakes  Equalizes pressure required for braking  Keeps the system full of fluid as the linings wear  May maintain a slight pressure to keep contaminants from entering the system

22 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brakes appliedBrakes released Master Cylinder

23 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Components

24 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Components  Cup and piston  used to pressurize the system  when they are pushed forward, they trap fluid, building pressure  Intake port  allows fluid to enter the rear of the cylinder as the piston slides forward  fluid flows from the reservoir, into the area behind the piston and cup

25 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Components  Compensating port  releases pressure when the piston returns to the released position  fluid can flow back into the reservoir through the compensating port  Residual pressure valves  maintain residual fluid pressure of approximately 10 psi (69 kPa) to help keep contaminants out of the system

26 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Components  Rubber boot  prevents dust, dirt, and moisture from entering the back of the master cylinder  Reservoir  stores an extra supply of brake fluid  cast as part of the housing or added as a removable plastic part

27 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Piston and Cup

28 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Residual Pressure Valve Brakes applied, fluid flows freely Brakes released, the valve closes to restrict the return of fluid to the master cylinder

29 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dual Master Cylinder

30 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dual Master Cylinder  Uses two separate hydraulic pistons and two fluid reservoirs  Each piston operates a hydraulic circuit that controls two wheel brake assemblies  If there is a leak in one of the hydraulic circuits, the other circuit can still provide braking action on two wheels

31 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dual Master Cylinder

32 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dual Master Cylinder (Normal Operation) Both pistons produce pressure to all four wheel brake assemblies

33 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Primary piston pushes on the secondary piston, two wheel brake assemblies still work Dual Master Cylinder (Rear Brake Circuit Leak)

34 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dual Master Cylinder (Front Brake Circuit Leak) Secondary piston slides forward, primary piston operates two wheel brakes normally

35 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Power Brakes  Use a booster and vacuum or hydraulic pressure to assist brake pedal application  The booster is located between the brake pedal linkage and the master cylinder  When the driver presses on the brake pedal, the brake booster helps push on the master cylinder pistons

36 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Vacuum Booster  Uses vacuum produced in the engine intake manifold or by a separate pump to apply the hydraulic brake system  Consists of a housing that encloses a diaphragm  When vacuum is applied to one side of the booster, the diaphragm moves toward the low-pressure area

37 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Vacuum Booster Operation

38 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Atmospheric Suspended Brake Booster  Atmospheric pressure is present on both sides of the diaphragm when the brakes are released  When the brakes are applied, vacuum is routed to one side of the booster  Atmospheric pressure then pushes on and moves the diaphragm

39 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Vacuum Suspended Brake Booster  Vacuum is present on both sides of the diaphragm when the brakes are released  When the brakes are applied, vacuum is released from one side of the booster  Atmospheric pressure then pushes on and moves the diaphragm

40 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Vacuum Brake Booster

41 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic Booster  Uses power steering pump pressure to help the driver apply the brake pedal  Known as hydro-boost or hydra-booster  Commonly used on vehicles with diesel engines  diesel engines do not produce a usable amount of intake manifold vacuum

42 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic Booster

43 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Hydraulic Booster When the pedal pushes on the unit, the spool valve allows more oil to enter the pressure chamber, pushing on the power piston

44 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Fluid  Specially blended hydraulic fluid that transfers pressure to the wheel brake assemblies  Rated by the SAE and DOT  SAE (Society of Automotive Engineers)  DOT (Department of Transportation)

45 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Fluid  Brake fluid must have the following characteristics:  correct viscosity at all temperatures  high boiling point  noncorrosive  water tolerant  lubricates components  low freezing point

46 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Lines and Hoses  Transfer fluid pressure from the master cylinder to the wheel brake assemblies  Lines  made of double-wall steel tubing  tubing ends usually have double-lap flares  Hoses  made of reinforced rubber  used where flexing action is necessary

47 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Lines and Hoses

48 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Line Hardware Brackets and clips secure the hoses and lines to prevent damage

49 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Systems Often used on rear- wheel-drive vehicles Often used on front- wheel-drive vehicles, with high front-to-rear brake ratio

50 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Disc Brake Assembly The assembly consists of a caliper, brake pads, a rotor, and hardware

51 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Single-Piston Caliper The caliper slides, as the piston moves in to clamp the brake pads against the rotor

52 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Fixed Caliper The caliper remains stationary, as pistons on each side clamp the rotor

53 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Caliper Assembly

54 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Caliper Components  Piston seal  prevents pressure leakage between the piston and the cylinder  helps pull the piston back into the cylinder when the brakes are not applied  Boot  prevents road dirt and water entry  Bleeder screw  allows air to be removed from the system

55 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Caliper Operation  When the brakes are applied, brake fluid flows into the caliper cylinder  Fluid pressure pushes the piston outward, forcing the brake pads into the rotor  When the brakes are released, the stretched piston seal pulls the piston back into the bore, as fluid pressure drops

56 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Caliper Operation Brakes appliedBrakes released

57 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Disc Brake Pads  Steel plates to which linings are riveted  Linings  made of heat-resistant organic or semimetallic friction material  semimetallic linings withstand higher temperatures without losing their frictional properties

58 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Disc Brake Pads  Anti-rattle clips  keep the brake pads from vibrating and rattling  Pad-wear sensor  metal tab on the brake pad  emits a loud squeal when it scrapes against the brake disc, which happens when the lining has worn too thin

59 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Disc (Rotor)  Uses friction from the brake pads to slow or stop wheel rotation  Normally made of cast iron  Constructed as part of the hub or as a separate unit  Can be solid or have a ventilated rib construction

60 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Disc Brake Assembly This rotor is vented to increase cooling

61 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Floating Caliper  The disc brake is mounted on two bolts supported by rubber bushings  Uses one piston  The caliper is free to shift, or float, in the rubber bushings

62 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Sliding Caliper  Uses one piston  Mounted in slots machined in the caliper adapter  The caliper is free to slide sideways in the slots as the linings wear

63 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Fixed Caliper  Uses more than one piston and caliper cylinder  The caliper is bolted directly to the steering knuckle  Pistons on both sides of the disc push against the brake pads

64 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Drum Brake Assembly A large drum surrounds the brake shoes and the hydraulic wheel cylinder

65 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Backing Plate  Holds the springs, wheel cylinder, and other parts inside the drum  Helps keep road dirt and water off the brakes  Bolts to the axle housing or the spindle support

66 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Uses master cylinder pressure to force the brake shoes out against the drum Wheel Cylinder Assembly

67 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Boots  keep road dirt and water out of the cylinder  Pistons  metal or plastic plungers that transfer force out of the cylinder to the brake shoes  Cups  rubber seals that keep fluid from leaking past the pistons Wheel Cylinder Components

68 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Wheel Cylinder Components  Springs  hold the rubber cups against the pistons when the wheel cylinder assembly is not pressurized  metal expanders may be used on the ends  Bleeder screw  provides a means of removing air from the brake system

69 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Shoes  Rub against the revolving brake drum to produce braking action  Made by fastening organic friction material onto a metal shoe  rivets or bonding agents may be used  The front shoe is the primary shoe  uses the shorter lining  The rear shoe is the secondary shoe  uses the larger lining surface area

70 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Shoes  Retracting springs  pull the brake shoes away from the brake drums when the brake pedal is released  Hold-down springs  hold the brake shoes against the backing plate when the brakes are in the released position

71 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Drum Brake Assembly

72 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Shoe Adjusters  Maintain the correct drum-to-lining clearance as the brake linings wear  Automatic adjusters normally function when the brakes are applied with the vehicle moving in reverse  If there is too much lining clearance, the brake shoes move outward and rotate with the drum enough to operate the adjusting lever

73 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Cable-type star wheel adjuster Brake Shoe Adjusters

74 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Link-type star wheel adjuster Brake Shoe Adjusters

75 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Lever-type star wheel adjuster Brake Shoe Adjusters

76 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Cable-type star wheel adjuster with an overtravel spring Brake Shoe Adjusters

77 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Lever-latch adjuster Brake Shoe Adjusters

78 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Sliding-latch adjuster Brake Shoe Adjusters

79 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Drums Provide a rubbing surface for the brake shoe linings

80 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Shoe Energization  When the brake shoes are forced against the rotating drum, they are pulled away from their pivot point by friction  This self-energizing action draws the shoes tighter against the drum  Servo action results when the primary shoe helps apply the secondary shoe

81 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Shoe Energization Self-Energizing Action Non-Servo Action Primary shoe is self-energized Servo Action Less hydraulic pressure is needed to apply the brakes

82 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Control Valves and Switches

83 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Stoplight Switch  Operates the rear brake lights  Normally open switch, usually mounted on the brake pedal mechanism  When the brake pedal is pressed, it closes the switch

84 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Warning Light Switch  Also called the pressure differential valve  Warns the driver of a pressure loss on one side of a dual brake system  If a leak develops in either the primary or secondary brake system, unequal pressure pushes the switch piston to one side, grounding the indicator circuit

85 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Warning Light Circuit

86 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Warning Light Switch Pressure difference pushes the piston to close the warning lamp circuit

87 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Low-Fluid Warning Light Switch  Turns on a dash light if the brake fluid in the master cylinder becomes low  Often mounts in the master cylinder lid or cover  Commonly operated by a float

88 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Metering Valve  Used to equalize braking action on vehicles with front-wheel disc brakes and rear-wheel drum brakes  Located in the line to the disc brakes  Prevents the front brakes from applying until pressure reaches approximately 75–135 psi (517–930 kPa)  This pressure overcomes the rear brake return springs

89 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Proportioning Valve  Used to equalize braking action on vehicles with front-wheel disc brakes and rear-wheel drum brakes  Located in the line to the drum brakes  Limits pressure at the rear drum brakes when high pressure is needed to apply the front disc brakes  Minimizes rear-wheel lockup during heavy braking

90 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Combination Valve  Single unit that functions as a brake warning light switch, a metering valve, and/or a proportioning valve  Common on late-model vehicles

91 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Combination Valve

92 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Incorporates a proportioning valve and a warning light switch

93 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

94 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Parking Brake Operation  When the hand or foot lever is activated, it pulls a steel cable that runs through a housing  The cable pulls on a lever inside the drum or disc brake assembly, forcing the brake linings against the rear drums or discs

95 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Parking Brake Components Foot-operated parking brake pedal A lever pushes the shoes against the drum

96 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Parking Brake Operation (Rear Disc Brakes)  A thrust screw and a lever can be added to the brake caliper  When the parking brake is applied, the cable pulls on the caliper lever  The caliper lever turns the thrust screw, which pushes on the caliper piston and applies the brake pads to the disc

97 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Rear Disc Brake Caliper Note the parking brake mechanism


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